An evaluation of Youth Guidance’s Becoming a Man (BAM) program, which mentors at-risk adolescent and teenage boys on Chicago’s South and West sides, found that the program significantly reduced violent crime while high-school graduations rose sharply among program participants. The evaluation, conducted by The University of Chicago Crime Lab, recipient of the MacArthur Award for Creative and Effective Institutions; Northwestern University; Harvard University; and the University of Pennsylvania, examined how the program affected thousands of students from 2009-2010 and 2013-2015. It showed that among participants, violent-crime arrests fell 50 percent, arrests for all types of crime fell 35 percent, and high-school graduation rates rose 19 percent. MacArthur supported early implementation and evaluation of BAM and provided support to Youth Guidance to consider options for expanding the program.